The present invention relates to a method of producing ink jet recording medium that uses a coating liquor for ink-receiving layer having porous inorganic composition as a major component. In more detail, it relates to a method of producing ink jet recording medium that allows to arbitrarily adjust the surface gloss of ink-receiving layer of ink jet recording medium.
The ink jet recording system, which lets fly fine droplets of ink by different action principles and allows them to attach onto the recording media such as paper to record images, letters, etc., is spreading rapidly over various applications, because of high speed, low noise, easy multicoloration and additionally unnecessity of development and fixation. Moreover, the images to be formed by multicolor ink jet system make it possible to afford comparable records compared even with multicolor prints by graphic arts system and printed pictures by color photograph system, and, in the use for making small number of copies, they are being applied widely even to the area of full color image recording, because of lower cost than those by photographic technologies.
Efforts have been made from the aspects of device and ink composition to use fine paper and coated paper used for usual printing and writing as the recording media to be used in said ink jet recording system. However, with the improvement in the performance of ink jet recording device such as higher speed, high preciseness or full coloration and the expansion of uses, higher characteristics have become to be required also for the recording media. Namely, as the recording media, those that the dot density of ink is high and the color tone is bright and vivid, that the absorption of ink is fast and the ink does not flow out or blur even when ink dots are superposed, and that the diffusion of ink in the lateral direction is not so much over the necessity and the periphery is smooth and does not become hazy, are required.
For solving these problems, some proposals have been presented so far. For example, in Japanese Unexamined Patent Publication No. Sho 52-53012, an ink jet recording paper with surface-converting coating provided on a low-sized base stock is disclosed, and, in Japanese Unexamined Patent Publication No. Sho 5349113, an ink jet recording paper with water-soluble high-molecular material impregnated into a sheet with urea-formalin resin powder added internally is disclosed. These ink jet recording papers of general paper type show fast ink absorption, but have drawbacks that the periphery of dots tends to become hazy and the dot density is also low.
Moreover, in Japanese Unexamined Patent Publication No. Sho 55-5830, an ink jet recording paper with ink-absorptive coating layer provided on the surface of supporter is disclosed, and, in Japanese Unexamined Patent Publication No. Sho 55-51581, an example that uses silica powder as a pigment in covering layer is disclosed. These ink jet recording papers of coated paper type show more improvement in the points of dot diameter, dot shape, dot density and reproduction of color tone that those of ink jet recording papers of general paper type, but, since the ink to be applied to these recording media is most often an aqueous ink using water-soluble dye, they have a problem that, when water etc. splash on the image formed on the recording media, the dye dissolves out again and exudes to remarkably lower the worth of recorded matter. So, for improving this drawback, Japanese Unexamined Patent Publication No. Sho 60-232990 disclosed an ink jet recording medium with porous cationic hydrated aluminum oxide allowed to contain in said ink-receiving layer, resulting in improved water resistance etc. This is paying an attention to the porosity of hydrated aluminum oxide and aims at taking the liquid substances such as ink and water into pores.
There, nowadays, the surface gloss of ink jet recording medium includes a variety of types from low gloss of general paper type to high gloss that replaces the photographic paper in color photography system or aims at the feeling of high quality for printed (recorded) image, which are chosen to suit the uses. As the means to achieve high-gloss surface, a method of obtaining high-gloss surface by passing between heated and pressurized roll nips of supercalender etc., a method of pressing the ink-receiving layer against heated mirror face in the wet state for drying (cast process referred to so in the production method of coated paper) as in Japanese Unexamined Patent Publication No. Hei 6-79967, and the like are disclosed.
However, with the ink jet recording medium with porous inorganic composition (e.g. species of alumina and silica) coated directly onto the supporter to form coated film as an ink-receiving layer, it is difficult to achieve high gloss surface by the methods as described above. That is, by the supercalender method, the effect for making high gloss is low because of hard coated film itself and the pores created with considerable effort end up to be collapsed, resulting in decreased ink absorption. In the case of cast process, there exist many restrictions in the viscosity, solids concentration, etc. of coating liquor to be applied onto the substrate to form the ink-receiving layer, so it is difficult in principle to increase the amount capable of coating. That is, the inorganic composition such as alumina sol extremely increases the viscosity at high solids concentration causing inconvenience as a coating liquor, hence it has the greatest defect that does not allow to increase the thickness of ink-receiving layer. For this reason, only thin ink-receiving layer can be formed, making it impossible to obtain good image quality. Moreover, when attempting to produce a plurality of ink jet recording media with different surface glosses, cast drums corresponding to respective glosses are required, leading to immense expenditure in the investment for installation.
The purpose of the invention is to provide a method of producing ink jet recording medium capable of easily and inexpensively creating an arbitrary gloss surface without injuring the image qualities (such as high dot density of ink, bright and vivid color tone, fast ink absorption and no flowing-out or blurring of ink), in the recording medium for recording with ink that uses a coating liquor for ink-receiving layer having porous inorganic composition as a major component.